Traditionally, to maintain a beverage at an elevated temperature, an insulated bottle or container is used. The insulation often comprises an evacuated space maintained between the inner and outer shells of the bottle to slow heat transfer but not eliminate it. Accordingly, over time and depending on the surround ambient conditions, the beverage contained in the bottle cools. Essentially, the effective use time of the insulated bottle is limited to several hours before the liquid contents cool to a temperature below a desired minimum.
Actively heated bottles and containers are known but the amount of energy required to heat the liquid contents and maintain the liquid at a desired temperature is significant. Typically, these types of container are used with insulation and employ AC electric heaters that need to be plugged into an outlet to operate. Using batteries to power the heater is just not practicable given the size and weight of the battery or batteries required to heat and maintain the liquids temperature for any reasonable period of time.